Energy efficient dryer systems

Abstract

A dryer including a housing, a drying chamber disposed within the housing, and a heating element coupled to the housing. The dryer further includes an intake configured to supply intake air to the drying chamber and an exhaust vent configured to vent exhaust air out of the drying chamber. The intake, the drying chamber, and the exhaust vent define an air flow path from the intake through the drying chamber and out the exhaust vent. The dryer includes a heat exchanger and a heat pump having a condenser. The heat exchanger and the heat pump are each configured to absorb thermal energy from the exhaust air and transfer the thermal energy to the intake air. The air flow path is configured such that the intake air is heated directly or indirectly by the heat exchanger prior to the intake air being further heated directly or indirectly by the condenser. The air flow path is configured such that the intake air is further heated directly or indirectly by the condenser prior to the intake air entering the drying chamber.

What is claimed: 
     
       1. A dryer comprising:
 a housing; 
 a tumbler; 
 a heating element coupled to the housing; 
 an intake configured to supply intake air to the tumbler; 
 an exhaust vent configured to vent exhaust air out of the tumbler; and 
 a heat pump having a condenser coupled to the tumbler; 
 wherein the intake, the tumbler and the exhaust vent define an air flow path from the intake through the tumbler and out the exhaust vent; 
 wherein air enters the dryer at the intake, and exits the dryer from the exhaust vent; 
 wherein the heat pump is configured to absorb thermal energy from the exhaust air; 
 wherein the condenser is configured to heat the intake air using the absorbed thermal energy; and 
 wherein the heating element is configured to heat the intake air. 
 
     
     
       2. The dryer of  claim 1  wherein the condenser is configured to transfer thermal energy to a heat exchanger, wherein the heat exchanger is configured to transfer thermal energy from the condenser to the tumbler. 
     
     
       3. The dryer of  claim 2  wherein the heat exchanger comprises a heat-pipe. 
     
     
       4. The dryer of  claim 1  wherein the heat pump includes an evaporator. 
     
     
       5. The dryer of  claim 4  wherein the air flow path is configured such that the exhaust air leaving the tumbler is cooled directly or indirectly by the evaporator prior to passing through the exhaust vent. 
     
     
       6. The dryer of  claim 1  wherein the condenser is further configured to provide heat to the intake air prior to the intake air entering the tumbler. 
     
     
       7. The dryer of  claim 1 , wherein the air flow path is configured to pass the intake air over the heating element after the intake air has been heated directly or indirectly by the heat pump. 
     
     
       8. The dryer of  claim 1  further comprising a controller configured to receive a user input corresponding to a mode of operation for the dryer, wherein the controller is configured to adjust the heating element and adjust an operating parameter of the heat pump in response to the user input. 
     
     
       9. The dryer of  claim 8  wherein the heat pump includes a compressor and an evaporator; wherein the operating parameter of the heat pump is a compressor pressure; and wherein the controller adjusts the compressor pressure in response to a feedback signal indicative of an air temperature. 
     
     
       10. The dryer of  claim 8  wherein the heat pump includes an expansion valve. 
     
     
       11. The dryer of  claim 10  wherein the controller is configured to modify an operation of the expansion valve.